I a have a multithread application (MIDAS) that makes uses of windows messages to communicate with itself.
MAIN FORM
The main form receives windows messages sent by the RDM LogData(‘DataToLog’)
Because windows messages are used they have the following attributes
QUESTION:
Can you Suggest a better way doing this without using windows messages ?
MAIN FORM CODE
const
UM_LOGDATA = WM_USER+1002;
type
TLogData = Record
Msg : TMsgNum;
Src : Integer;
Data : String;
end;
PLogData = ^TLogData;
TfrmMain = class(TForm)
//
private
procedure LogData(var Message: TMessage); message UM_LOGDATA;
public
//
end;
procedure TfrmMain.LogData(var Message: TMessage);
var LData : PLogData;
begin
LData := PLogData(Message.LParam);
SaveData(LData.Msg,LData.Src,LData.Data);
Dispose(LData);
end;
RDM CODE
procedure TPostBoxRdm.LogData(DataToLog : String);
var
WMsg : TMessage;
LData : PLogData;
Msg : TMsgNum;
begin
Msg := MSG_POSTBOX_RDM;
WMsg.LParamLo := Integer(Msg);
WMsg.LParamHi := Length(DataToLog);
new(LData);
LData.Msg := Msg;
LData.Src := 255;
LData.Data := DataToLog;
WMsg.LParam := Integer(LData);
PostMessage(frmMain.Handle, UM_LOGDATA, Integer(Msg), WMsg.LParam);
end;
EDIT:
Why I want to get rid of the windows messages:
Use Named Pipes. If you don't know how to use them, then now is the time to learn.
With named pipes, you can send any type of data structure (as long as both the server and the client know what that data structure is). I usually use an array of records to send large collections of info back and forth. Very handy.
I use Russell Libby's free (and open-source) named pipe components. Comes with a TPipeServer and a TPipeClient visual component. They make using named pipes incredibly easy, and named pipes are great for inter-process communication (IPC).
You can get the component here. The description from the source is: // Description : Set of client and server named pipe components for Delphi, as // well a console pipe redirection component.
Also, Russell helped me out on Experts-Exchange with using an older version of this component to work in a console app to send/receive messages over named pipes. This may help as a guide in getting you up and running with using his components. Please note, that in a VCL app or service, you don't need to write your own message loop as I did in this console app.
program CmdClient;
{$APPTYPE CONSOLE}
uses
Windows, Messages, SysUtils, Pipes;
type
TPipeEventHandler = class(TObject)
public
procedure OnPipeSent(Sender: TObject; Pipe: HPIPE; Size: DWORD);
end;
procedure TPipeEventHandler.OnPipeSent(Sender: TObject; Pipe: HPIPE; Size: DWORD);
begin
WriteLn('On Pipe Sent has executed!');
end;
var
lpMsg: TMsg;
WideChars: Array [0..255] of WideChar;
myString: String;
iLength: Integer;
pcHandler: TPipeClient;
peHandler: TPipeEventHandler;
begin
// Create message queue for application
PeekMessage(lpMsg, 0, WM_USER, WM_USER, PM_NOREMOVE);
// Create client pipe handler
pcHandler:=TPipeClient.CreateUnowned;
// Resource protection
try
// Create event handler
peHandler:=TPipeEventHandler.Create;
// Resource protection
try
// Setup clien pipe
pcHandler.PipeName:='myNamedPipe';
pcHandler.ServerName:='.';
pcHandler.OnPipeSent:=peHandler.OnPipeSent;
// Resource protection
try
// Connect
if pcHandler.Connect(5000) then
begin
// Dispatch messages for pipe client
while PeekMessage(lpMsg, 0, 0, 0, PM_REMOVE) do DispatchMessage(lpMsg);
// Setup for send
myString:='the message I am sending';
iLength:=Length(myString) + 1;
StringToWideChar(myString, wideChars, iLength);
// Send pipe message
if pcHandler.Write(wideChars, iLength * 2) then
begin
// Flush the pipe buffers
pcHandler.FlushPipeBuffers;
// Get the message
if GetMessage(lpMsg, pcHandler.WindowHandle, 0, 0) then DispatchMessage(lpMsg);
end;
end
else
// Failed to connect
WriteLn('Failed to connect to ', pcHandler.PipeName);
finally
// Show complete
Write('Complete...');
// Delay
ReadLn;
end;
finally
// Disconnect event handler
pcHandler.OnPipeSent:=nil;
// Free event handler
peHandler.Free;
end;
finally
// Free pipe client
pcHandler.Free;
end;
end.